The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a balloon catheter to be inserted into a stenosis site inside a blood vessel for expanding the stenosis site.
Balloon catheters to be inserted into a stenosis site inside a blood vessel for expanding the stenosis site have already been proposed. A balloon catheter mainly comprises a balloon as an expanding body, an outer shaft joined to a proximal end of the balloon, and an inner shaft inserted within the balloon and the outer shaft. Further, a metal marker member having radiopacity is commonly provided inside the balloon so that the position of the balloon can be detected under exposure of irradiation.
For example, Japanese Patent No. 3659664 discloses a catheter for expanding a blood vessel. The catheter includes a platinum contrast marker (a marker member) attached to a medical tube (an inner shaft) comprising an inner layer, a coil layer as a reinforcement layer, and an outer layer.
As another example, Japanese Patent No. 3219968 discloses a balloon-expandable catheter having an inner tube (an inner shaft) and a balloon. A radiopaque marker fits in the inside of a depressed groove arranged on an outer periphery of the inner tube in the inside of the balloon. The radiopaque marker is covered by a heat-shrinkable tube. Moreover, also disclosed is a balloon-expandable catheter in which the radiopaque marker is arranged on the outer periphery of an inner tube not having a depressed groove. Here too, the radiopaque marker is covered by a heat-shrinkable tube.
However, the catheter for expanding a blood vessel disclosed in Japanese Patent No. 3659664 has the following disadvantages. Since the marker member is attached to the outer periphery of the inner shaft and is exposed to an inner periphery of the balloon, there is a risk that an end portion of the marker member may damage the balloon. Further, a difference in rigidity may arise when a flexible inner shaft and a highly rigid marker member are used, creating a risk that the inner shaft will buckle due to an excessively concentrated stress at the attachment position of the marker member.
Moreover, in the balloon-expandable catheter disclosed in Japanese Patent No. 3219968 above, processing steps such as polishing and etching are required for providing a depressed groove. Therefore, the manufacturing process will be disadvantageously complicated. Further, disadvantageously, a site where the depressed groove is provided tends to have decreased strength due to the reduction in cross-sectional area. Furthermore, since the outer diameter of a balloon portion will be larger for a configuration in which the radiopaque marker is arranged on the outer periphery of the inner tube and is covered by a heat-shrinkable tube, the diameter of the balloon catheter cannot be easily reduced. Further, disadvantageously, in a case where the marker member is made of a highly rigid metal, the marker member itself cannot be easily deformed as required to follow the curvature of a blood vessel and the like, and the portion of the balloon catheter at which the marker member is arranged may easily become stuck in the blood vessel.